a. Field of the Invention
The present invention pertains to data storage systems and more specifically to the mechanical configuration of data storage systems having multiple disk drives.
b. Description of the Background
Storage systems with multiple disk drives are a mainstay of modern data storage systems. Technology such as RAID, Redundant Array of Independent Disks, is being commercialized into many different platforms. In very high capacity disk storage systems, it is desirable to have as much storage in as small a space as possible. Typically, very large data storage systems may be rack mounted and afford some serviceability for the disk drives, as the disk drives are often a point of failure for the system. The disk drive is considered a point of failure because an internal mechanical failure of the disk drive has a high likelihood of being catastrophic where all the data from the disk drive may be lost.
RAID technology incorporates two main techniques for ensuring that data is not lost in the event of a single disk failure. The first technique is mirroring wherein a complete copy of all the data on one disk is kept on a second disk. The mirroring technique is known generically as RAID 1. The second technique is where data from multiple disks may be used to compute parity data that is stored on another disk. In the event of a single disk failure, the failed disk may be replaced and reconstructed using the data of the other drives and the parity data. The parity technique is known in various forms, with popular forms being known as RAID 3 or RAID 5.
Many systems utilize both mirroring and parity techniques to ensure the recoverability of the data. For example, a system may include two identical sets of RAID 5 disk arrays may be set up as a mirror of each other. A mirrored system may allow one half of the system to be serviced while the other half performs all of the data serving duties without having to shut off the entire system. Another benefit of mirrored systems is to minimize the number of single points of failure for the entire system. By having a redundant set of components, the failure of one of the components may allow the system to operate while service is pending or being performed.
In some storage solutions, many disk drives are used to store data. Each disk drive may be replaceable in the event of failure. In making each disk drive individually replaceable, a rack mounted storage system may occupy a large amount of vertical rack space while underutilizing the depth of the rack. Such systems may not efficiently use the rack space.
It would therefore be advantageous to provide a disk array that was compact while housing a high number of disk drives. It would be further advantageous to provide a disk array that minimized the number of single points of failure for the entire disk array system. It would be still further advantageous to provide a disk array that was easily and quickly serviceable.